The Philippines is an amazing country in geological terms, as it is spread over 7,000 islands, and covers thousands of square miles. Usually when there is a long distance between the north and the south of the country, it means the climate is different. Take the USA for instance, it is hot and dry down the south, while the northern states suffer from cold winters and a lot of rain. However, this is not really the case with the Philippines, although there are differences in the climate between regions, but nothing as extreme as the USA.
As the Philippines is close to the equator, it means the weather is always hot and humid. As it is really an island surrounded by water, this explains why the area constantly has a high rate of humidity, usually in the region of 80%+. This is uncomfortable for many tourists, especially for those who sweat a lot, or have difficulty handling the heat. Ninety degrees in Death Valley, Nevada, is much easier to handle than the same temperature in Manila.
The difference in climate between the likes of Manila and Davao are not really noticeable, even though they are split by hundreds of miles. It does mean that both areas tend to receive different types of weather. The south eastern parts of the Philippines are often hit by typhoons as they move in from the Pacific Ocean. These have caused a number of disasters in recent years. Although these storms can still hit places like Manila, they have usually lost their power when it comes to the wind, but they can still dump a lot of water.
The Philippines also has a summer and rainy season. With the former being around May, and is probably the time best avoided by tourists, as humidity can get really high. With the average temperature around the world increasing due to climate change, the number of typhoons and intensity has been increasing. This means that it is worth checking the average weather conditions for the area you intend to visit prior to making a booking.